Jun 242018
 
An enhanced set of displacement parameter restraints in CRYSTALS (P. Parois, J. Arnold and R.I. Cooper)

Journal of Applied Crystallography, 2018, 51. [ doi: 10.1107/S1600576718007100 ]

The implementation and use of a set of new displacement parameter restraints is described. Anisotropic displacement parameters account for a large proportion of the parameters in a crystallographic refinement, but very few restraints for conveniently controlling their values have been implemented in standard … Read the rest

Nov 012017
 
Some Experimental Aspects of Absolute Configuration Determination using Single Crystal X-​Ray Diffraction (A. L. Thompson, S. F. Jenkinson & G. W. J. Fleet)

Tetrahedron Asymmetry 2017, 28(10), 1330-1336 [doi:10.1016/j.tetasy.2017.08.016]

Students of single crystal X-​ray diffraction are often give advice as to how best to collect their data when attempting absolute configuration determination.  These ‘rules’ often have more grounding in gut-​feeling than evidence.  Thus, in an effort to provide advice and evidence that today’s crystallographers can … Read the rest

Oct 232017
 
HUG and SQUEEZE: using CRYSTALS to incorporate resonant-scattering in the SQUEEZE structure factor contributions to determine absolute structure (R.I. Cooper, H.D. Flack and D.J. Watkin)Acta Crystallographica, 2017, C73, 845–853. [ doi:10.1107/S2053229617013304 ] Using an approximate correction to the X-ray scattering from disordered, resonantly scattering regions of crystal structures we have developed and tested a procedure (HUG) to recover the absolute structure using conventional Flack x refi nement or other post-re finement determination methods.
Jul 062017
 
Will They Co-crystallize? (J.G.P. Wicker,  L.M. Crowley,  O. Robshaw,  E.J. Little,  S. Stokes,  R.I. Cooper  and  S.E. Lawrence)

CrystEngComm, 2017, 19, 5336 – 5340 [ doi:10.1039/C7CE00587C ]

A data-driven approach to predicting co-crystal formation reduces the number of experiments required to successfully produce new co-crystals. A machine learning algorithm trained on an in-house set of co-crystallization experiments results in a 2.6-fold enrichment of successful co-crystal formation in a ranked list of … Read the rest

Jun 202017
 
A publicly available crystallisation data set and its application in machine learning (M. Pillong, C. Marx, P. Piechon, J.G.P. Wicker, R.I. Cooper and T. Wagner)

CrystEngComm, 2017,19, 3737-3745 [ doi:10.1039/C7CE00738H ]

We present here the crystallisation outcomes for 319 publicly available compounds in up to 18 different solvents spread over 5710 individual single solvent evaporation trials. The recorded data is part of a much larger, corresponding in-house database and includes both positive as well as negative crystallisation … Read the rest

Nov 242016
 
Beyond Rotatable Bond Counts: Capturing 3D Conformational Flexibility in a Single Descriptor (J.G.P. Wicker and R.I. Cooper)J. Chem. Inf. Model., 2016, 56 (12), 2347–2352 doi: 10.1021/acs.jcim.6b00565 A new molecular descriptor, nConf20, based on chemical connectivity, is presented which captures the accessible conformational space of a molecule. Currently the best available 2-dimensional descriptors for quantifying the flexibility of a particular molecule are the rotatable bond count (RBC) and the Kier flexibility index.
Sep 232016
 
Hydrogen-​Bonded Homoleptic Fluoride-​Diarylurea Complexes: Structure, Reactivity, and Coordinating Power (L. Pfeifer, K. M. Engle, G. W. Pidgeon, H. A. Sparkes, A. L. Thompson, J. M. Brown & V. Gouverneur)

Journal of the American Chemical Society 2016, 138(40), 13314-13325 [doi:10.1021/jacs.6b07501]

Hydrogen bonding with fluoride is a key interaction encountered when analyzing the mode of action of 5′-​fluoro-​5′-​deoxyadenosine synthase, the only known enzyme capable of catalyzing the formation of a C-​F bond from F​. Further understanding of the effect … Read the rest

Sep 192016
 
Why direct and post-refinement determinations of absolute structure may give different results (D.J. Watkin and R.I. Cooper)

Acta. Cryst. (2016) B72 661-683 (Feature Article) [ doi:10.1107/S2052520616012890 ]

Direct determination of the Flack parameter as part of the structure refinement procedure usually gives different, though similar, values to post-refinement methods. The source of this discrepancy has been probed by analysing a range of data sets taken from the recent literature. Most significantly, … Read the rest

Aug 022016
 
Report on the sixth blind test of organic crystal structure prediction methods (A. M. Reilly, R. I. Cooper, C. S. Adjiman, S. Bhattacharya, A. D. Boese ...

Acta. Cryst. (2016) B72(4), 439-459 [ doi:10.1107/S2052520616007447 ] A. M. Reilly, R. I. Cooper, C. S. Adjiman, S. Bhattacharya, A. D. Boese, J. G. Brandenburg, P. J. Bygrave, R. Bylsma, J. E. Campbell, R. Car, D. H. Case, R. Chadha, J. C. Cole, K. Cosburn, H. M. Cuppen, F. Curtis, G. M. Day, … Read the rest

Mar 072016
 
Absolute structure determination using CRYSTALS (R.I. Cooper, D.J. Watkin and H.D. Flack)

Acta. Cryst. (2016) C72, 261-267 [ doi:10.1107/S2053229616003570 ]

A study of post-refinement absolute structure determination using previously published data was carried out using the CRYSTALS software package. We show that absolute structure determination may be carried out optimally using the analyses available in CRYSTALS, and that it is not necessary to have the … Read the rest